Glimpses of Ocean Life 29

Glimpses of Ocean Life 29

The instruments can all be withdrawn into the body of the animal at

will, but we can easily conceive that such formidable weapons being

retracted into its flesh would not add to the creature's comfort--in

fact they would produce a deadly effect, were it not for the following

simple and beautiful contrivance.

 

Each spine is furnished with a double sheath composed of two blades,

between which it is lodged; these sheaths closing upon the sharp points

of the spear when the latter is drawn inwards, effectually guard the

surrounding flesh from injury.

 

The shape of this animal is oval, the back convex, while the under part

presents a flat and curious ribbed-like appearance. Its length varies

from three to five inches; specimens, however, are sometimes to be

procured, even on our own shores, of much larger dimensions.

 

 

 

 

CHAPTER XVIII.

 

Star-fishes.

 

(OPHIURIDAE AND ASTERIADAE.)

 

 

'As there are stars in the sky, so there are stars in the sea.'--LINK.

 

 

 

 

XVIII.

 

 

There are not a few persons still to be met with, who believe that

man and the lower animals appeared simultaneously upon the face of

the earth. Geology most forcibly proves the error of such an idea,

for although the fossilized remains of every other class of organized

beings have been discovered, human bones have nowhere been found.

This fact, though deeply interesting, is perhaps not more so than

many others which this wonderful science has unfolded. What can be

more startling to the student for instance, than the information that

for a long period, it may be thousands of years, no species of fish

whatever inhabited the primeval seas? True it is that certain creatures

occupied the shallows and depths of ocean, but these were of the lowest

type. The most conspicuous were the coral polypes, which even then as

now were ever industriously building up lasting monuments of their

existence, as the Trilobites, a group of Crustacea, and the Crinoids,

or Lily-stars.

 

The last-mentioned group of animals were analogous to the present tribe

of Star-fishes, and are now nearly extinct. The body of the Lily-star,

which resembled some beautiful radiate flower, was affixed to a long,

slender stalk, composed of a series of solid plates superposed upon

one another, bound together by a fleshy coat, and made to undulate

to and fro in any direction at the will of the animal. The stalk

was firmly attached to some foreign substance, and consequently the

Crinoid Star-fish, unlike its modern representative, could not rove

about in search of prey, but only capture such objects as came within

reach of its widely expanded arms. 'Scarcely a dozen kinds of these

beautiful creatures,' observes Professor Forbes, 'now live in the seas

of our globe, and individuals of these kinds are comparatively rarely

to be met with; formerly they were among the most numerous of the

ocean's inhabitants,--so numerous that the remains of their skeletons

constitute great tracts of the dry land as it now appears. For miles

and miles we may walk over the stony fragments of the Crinoidae,

fragments which were once built up in animated forms, encased in

living flesh, and obeying the will of creatures among the loveliest

of the inhabitants of the ocean. Even in their present disjointed and

petrified state, they excite the admiration not only of the naturalist,

but of the common gazer; and the name of stone lily, popularly applied

to them, indicates a popular appreciation of their beauty.' Each

wheel-like joint of the fossil Encrinite being generally perforated

in the centre, facility is thus afforded for stringing a number of

these objects together like beads, and in this form the monks of old,

according to tradition, used the broken fragments of the lily-stars as

rosaries. Hence the common appellation of St Cuthbert's Beads, to which

Sir Walter Scott alludes,--

 

'On a rock by Lindisfarn

St. Cuthbert sits, and toils to frame

The sea-born beads that bear his name.'

 

One solitary species of the Crinoid Star-fishes has of late years been

found to flourish in our own seas; it is, however, affixed to a stalk

(pedunculated) only in the early periods of its existence.

 

When first discovered by Mr. Thompson in its infant state, the

_Pentacrinus Europæus_ was believed to be a distinct animal. It was

taken attached to the stems of zoophytes of different orders, and

measured about three-fourths of an inch in height. In form it resembled

a minute comatula mounted on the stalk of a Pentacrinus. Subsequent

research has proved that the little stranger was merely the young state

of the feather star _Comatula rosacea_, and that although for a certain

period attached to a slender waving stem, the Pentacrinus, when arrived

at a certain stage of development, feels fully able to start life on

its own accord, and hence takes opportunity to break off its early

ties, and become a free animal, dependent upon its own exertions for

subsistence.

 

It is no uncommon thing, as a late writer forcibly remarks, in the

inferior classes of the animal kingdom, to find animals permanently

attached from the period of their birth, and during all their

existence. Familiar examples of this occur in the oyster, and various

other bivalve shell-fish, as well as in numerous compound zoophytes. We

likewise meet with races which are free and locomotive in their first

stages, and afterwards become permanently fixed; but an animal growing

for a period in the similitude of a flower on a stem, and then dropping

from its pedicle, and becoming during the remainder of its life free

and peripatetic, is not only new, but without any parellel in the whole

range of the organized creation.

 

The Comatula, or as it is commonly called, the Rosy Feather-star, is

allowed to be without exception the most lively of all the star-fishes.

Its movements in swimming are said to resemble exactly the alternating

strokes given by the medusa to the liquid element, and have the same

effect, causing the animal to raise itself from the bottom, and to

advance back foremost even more rapidly than the medusa. It has ten

very slender rays with numbers of long beards on the sides. The body,

which is of a deep rose colour, is small and surrounded with ten little

filiform rays. The extremities of these organs are shaped like claws,

by means of which the animal attaches itself to various kinds of

sea-weed, and other submarine objects.

 

The adult Comatula generally measures about five inches across its

fully expanded rays.

 

Before treating of what are termed the _true_ Star-fishes, we require

to dwell briefly upon an intermediate family named by Professor Forbes

the _Ophiuridæ_, 'from the long serpent or worm-like arms, which are

appended to their round, depressed, urchin like bodies.... They hold

the same relation to the Crinoidea that the true Star-fishes hold to

the Sea-Urchins. They are spinigrade animals, and have no true suckers

by which to walk, their progression being effected (and with great

facility) by means of five long flexible-jointed processes placed at

regular distances around their body, and furnished with spines on the

sides and membraneous tentacula. These processes are very different

from the arms of the true Star-fishes, which are lobes of the animal's

body, whereas the arms of the Ophiuridæ are super-added to the body,

and there is no excavation in them for any longation of the digestive

organs.'[16]

 

[16] British Star-fishes.

 

The British Ophiuridæ are now classed under two genera; of the Ophiuræ,

or Sand-stars only two species (_O. texturata_ and _O. albida_) are

found on our shores; and the Ophicomæ, or Brittle-stars, of which there

are ten.

 

An extraordinary feature, characteristic of all the above-mentioned

animals, is the great tendency which they have to mutilate themselves,

and throw their limbs about in fragments on the slightest provocation.

If a specimen be handled, a certain number of fragments will assuredly

be cast off. If the rays become entangled in sea-weed, or even if the

water in which the animal resides happens to become impure, the same

disastrous result follows, until nothing but the little circular disc

remains. As a set off against this weakness, both the Ophiuræ and the

Brittle-stars possess reproductive powers of a high order. Hence it not

unfrequently happens that if each and all the rays of a specimen be

rejected, the animal will live on, and eventually, perhaps, become a

complete and perfect star-fish.

 

The best means of preserving an Ophiura is to let the devoted animal

remain for a time expanded in sea-water, then with a small pair of

forceps lift it carefully up, and plump it into a bath of cold 'fresh'

water, letting it lie there for about an hour. The animal speedily

dies, as if poisoned, in the fresh liquid, in a state of rigid

expansion. Some writers recommend that, at this stage, the specimen

should be dipped for a moment into boiling water, and then dried in a

current of air; but I have never been able to detect any great benefit

arising from the adoption of the process.

 

When examining any of the Brittle-stars, I have always found it an

excellent plan to raise them up by aid of the forceps applied to the

disc. By this means a specimen may be moved about without any fear

of mutilation; whereas if the fingers be used as forceps, an unhappy

result will assuredly follow.

 

The _Ophiocoma rosula_, figured on Plate 9, will serve to convey to

the reader a general idea of this class of animals. Its popular title

is the Common Brittle-star, indicative of the inherent fragility of the

species, as also of their prevalent appearance at the sea-shore; but,

though so exceedingly 'common,' we must at the same time in justice

add, that the _O. rosula_ exceeds in beauty many other species which

are rare, and consequently more highly prized by the collector.

 

It is very abundant on all parts of the British coast, and is often

found in clusters upon the stems of _L. digitata_, and as frequently

upon the under side of boulders. In dredging, the Brittle-star is an

unfailing prize. It is a marvellous sight when the scrapings of the

ocean bed are spread out upon the dredging-board for examination,

to see hundreds of these singularly delicate creatures twisting and

twining about in all directions,--over each other's bodies, through the

weed, sand, shells, and mud, and strewing fragments of their snake-like

arms upon every surrounding object.

 

At the mere mention of 'Star-fishes,' the most uninitiated reader will

at once realize in his mind's eye a tolerably correct notion of the

form of these curious productions of the marine animal kingdom, even

although he had never seen a living or dead specimen.

 

The body of the animal is divided into rays, like the pictured form of

one of the heavenly stars, and the fancied resemblance is most apparent

in the Asteridæ, or true Star-fishes, of which we are now about to speak.